Liquid crystal display panel

ABSTRACT

The invention relates to an LCD panel for preventing the generation of blur due to ionic impurities. The LCD panel comprises a first substrate having a common electrode; a second substrate having an active area; a seal pattern along the periphery of said active area between said first substrate and said second substrate; a liquid crystal layer between said first substrate and said second substrate in said active area; and an electrode pattern between said seal pattern and said second substrate. Alternatively, the seal pattern has outwardly projecting corner portions. An electric field is generated between the electrode pattern and the common electrode so that the ionic impurities are prevented from penetrating into the active area, and the ionic impurities in liquid crystal are captured in the seal pattern portion to prevent the generation of blur due to ionic impurities.

This is a divisional application of application Ser. No. 09/941,628filed on Aug. 30, 2001 now U.S. Pat. No. 6,839,122. The presentinvention claims the benefit of Korean Patent Application No.P2000-69455 filed in Korea on Nov. 22, 2000, which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, moreparticularly, to a liquid crystal display panel in which blur due toionic impurities generated during the sealing process is avoided.

2. Background of the Related Art

In general, the liquid crystal display (LCD) panel comprises upper andlower glass substrates with liquid crystal sealed in between the upperand lower glass substrates.

The lower glass substrate has a plurality of gate lines arranged in onedirection with a certain distance between them and data lines arrangedalong another direction perpendicular to said gate lines with a certaindistance between them to define rectangular pixel areas arranged in amatrix. Each of the pixel areas includes a thin film transistor (TFT)which has a gate electrode connected to one of the gate lines, a sourceelectrode connected to one of the data lines, and a drain electrodeconnected to one of the pixel electrodes.

The upper glass substrate has a black matrix, a color filter layer andcommon electrode formed thereon.

The lower glass substrate and the upper glass substrate, as describedabove, are attached, leaving a space between the substrates, using asealing material (sealant) in a seal pattern along the periphery of thesubstrates. Liquid crystal is then injected into the space between theupper and lower glass substrates.

A seal pattern of related art used for sealing the upper and lower glasssubstrates together will be described in reference to the FIGS. 1, 2 and3.

FIG. 1 is a plan view of a seal pattern in a sealing area between upperand lower transparent substrates of the related art. FIG. 2 is amagnification of a part B in FIG. 1, and FIG. 3 is a partial sectionalview of part C in FIG. 1.

As described above, the lower substrate 2 having signal lines (notshown), pixel electrodes 3 and TFTs (not shown) is attached to the uppersubstrate 1 having a black matrix (not shown), a color filter layer (notshown) and common electrode 4. The lower substrate 2 is spaced apredetermined distance from the upper substrate 1 by a seal pattern S.Liquid crystal is injected into an active area A of the LCD and then thearea where the liquid crystal was injected is sealed by a sealing agentE, as shown in FIG. 1.

In other words, the upper and lower glass substrates are put togetherafter printing the seal pattern S in an outline portion of the activearea of the upper or lower glass substrate by a silk screen printingthrough a seal mask, and then liquid crystal is injected through aninjection hole, which is followed by sealing the injection hole with thesealing agent E.

The corner portions of the seal pattern S are substantially aperpendicular rectangular shape as shown in FIG. 2.

The seal pattern of the related art LCD has the following problems:

First, impurity ions existing on the surfaces of the substrates arecarried by the surface of the liquid crystal in a capillary phenomenonwhen the liquid crystal is injected in between the substrates.Accordingly, the impurity ions (e-) are deposited at the corner portionsof the display panel in relatively larger amounts. Such impurity ions(e-) are activated at a high temperature of about 50 degrees andgenerate blurs at the corner portions of an operating LCD.

Second, ionic impurities existing within the seal pattern can migrateinto the liquid crystal causing electric field distortion and thusgenerating blur in the active area A of a LCD. In other words, when theelectric field is applied between the common electrode 4 and the pixelelectrode 3 to induce the liquid crystal to have a different alignment,the pre-existing ionic impurities (e-) in the seal pattern can penetrateinto the liquid crystal in the active area A. The ionic impurities (e-)can then be adsorbed into the surface of the common electrode 4 andfunction as resistance components, so that electric field distortionwill take place and result in blur in the active area A.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a Liquid CrystalDisplay (LCD) panel that substantially obviates one or more of theproblems due to limitations and disadvantages of the related art.

An object of the invention is to provide an LCD panel in whichelectrodes are arranged so that the electrodes can apply voltage to thelower part of a seal pattern to prevent ionic impurities frompenetrating into an active area and to capture ionic impurities from theactive areas.

Also, it is another object of the invention to provide an LCD panel thatprovides spaces or projections in corner portions of a seal pattern tocollect impurities within the panel so that the generation of blur inthe corner portions of an LCD panel can be prevented.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, theLCD-panel includes a first substrate having a common electrode; a secondsubstrate having an active area; a seal pattern formed peripherally tosaid active area, and between said first substrate and said secondsubstrate; a liquid crystal layer between said first substrate and saidsecond substrate, and on the active area; and an electrode patternadjacent to said seal pattern and outside said active area.

In another aspect, the LCD panel includes a first substrate having acommon electrode; a second substrate having an active area; a sealpattern formed peripherally to said active area between said firstsubstrate and said second substrate, and having projected cornerportions; and a liquid crystal layer between said first substrate andsaid second substrate in said active area.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 is a plan view of a seal pattern in a sealing area between upperand lower transparent substrates of the related art;

FIG. 2 is a magnification of a part B in FIG. 1;

FIG. 3 is a partial sectional view of part C in FIG. 1;

FIG. 4 is a plan view of a seal pattern according to the firstembodiment of the present invention;

FIG. 5 is a sectional view of a part D in FIG. 4; and

FIG. 6 is a plan view of a seal pattern according to the secondembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

FIG. 4 is a plan view of a seal pattern according to the firstembodiment of the present invention, FIG. 5 is a sectional view of apart D in FIG. 4, and FIG. 6 is a plan view of a seal pattern accordingto the second embodiment of the present invention.

As shown in FIG. 4 and FIG. 5, after being printed with a seal pattern Shaving an injection hole, a lower glass substrate 2 is put together withan upper glass substrate 1 with a predetermined distance separating thesubstrates. The seal pattern S is coated on the lower substrate 2 by asilk screen printing using a seal mask so as to outline the active areaA of the LCD panel. After injecting liquid crystal through the injectionhole of the seal pattern, the injection hole is then closed with asealing agent E.

The lower substrate 2 has, not shown in the drawings, a plurality ofgate lines (not shown) arranged with a predetermined distance separatingthem, an insulation film (not shown) for insulating the gate lines, aplurality of data lines (not shown) arranged on the insulation film witha predetermined distance separating them in a direction perpendicular tothe gate lines, and a plurality of TFTs (not shown). The plurality ofdata lines and gate lines defining pixel areas form a matrix-shapedarrangement. Where each of the pixel areas has a TFT where the gatelines and the data lines intersect for transferring data signals of thedata lines to each corresponding pixel electrode in response to signalsof the gate lines. Also, a protective film 6 is formed to insulate eachof the TFTs and each of the data lines. The pixel electrode 3 in eachpixel area is formed on the protective film 6 and electrically connectedwith drain electrode. The portion of the lower substrate in which thegate lines and the data lines intersect to define pixel areas is anactive area A, and a seal pattern S is formed along the periphery of theactive area A.

Also, a black matrix (not shown in the drawings), a color filter layer(not shown) and transparent common electrode 4 are formed in the uppersubstrate 1.

An electrode pattern 5 is formed between the seal pattern and theprotective film 6 of the lower glass substrate 2 to capture ionicimpurities within the seal pattern S. The electrode pattern 5 may alsobe formed for the injection hole or on an adjacent portion of the lowersubstrate 2 outside the seal pattern. When simultaneously formed of thesame material as the pixel electrodes 3, the electrode pattern 5 can beformed without adding an additional process step.

In the alternative, the device of the present invention can have a colorfilter on transistor (COT) structure in which the color filter layer isformed above the TFT on the lower substrate, or a substrate having atransistor on color filter (TOC) structure in which the color filter isformed below the TFT on the lower substrate.

After the electrode pattern 5 is arranged in the seal pattern S formedas described above, an electric field is applied between the commonelectrode 4 and the pixel electrodes 3, and between the common electrode4 and the electrode pattern 5. The molecular arrangement of liquidcrystal layer in the active area A is changed due to the generation ofthe electric field between the pixel electrodes 3 and the commonelectrode 4. Also at the same time, due to the electric field betweenthe common electrode 4 and the electrode pattern 5, the ionic impuritiese− in or at the seal pattern are prevented from penetrating into theactive area A, and ionic impurities e− in the liquid crystal of theactive area A are captured within the seal pattern S.

The voltage applied between the common electrode 4 and the pixelelectrode 3 can be different than the voltage between the commonelectrode 4 and the electrode pattern 5. Therefore, an additional DCbias can be applied to the electrode pattern 5, or a common voltageapplied to the common electrode 4 can be stepped down in application.The common voltage applied to the common electrode 4 can be reversed inpolarity in application in the case of dot inversion operation and theelectrode pattern 5 should be at a voltage that will collect the ionicimpurities. Also the voltage of the electrode pattern 5 can have apolarity reversed from that of the voltage applied to said commonelectrode 4.

The LCD panel according to the second embodiment of the inventionincludes an upper substrate and a lower substrate put together with aseal pattern S having a structure with projected corner portions in theseal area between the substrates, as shown in FIG. 6.

As described in the related art, the corner portions are areas with ahigh density of ionic impurities since preexisting ionic impuritieswithin the panel are carried to the corner portions of the seal patternby the injected liquid crystal. Therefore, the corner portions of theseal pattern S according to the second embodiment of the presentinvention are outwardly projected so that the ionic impurities can becollected within the projected portions at the corners of the sealpattern.

Of course, as in the first embodiment of the invention, it is alsoeffective to form the electrode pattern 5 between the seal pattern S andthe lower substrate or on portions of the lower substrate adjacent tothe seal pattern S. Also, the electrode pattern 5 can be formed on thelower substrate where an injection hole sealant is positioned.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the LCD panel of the presentinvention without departing from the spirit or scope of the invention.Thus, it is intended that the present invention cover the modificationsand variations of this invention provided they come within the scope ofthe appended clams and their equivalents.

1. A liquid crystal display device comprising: a first substrate havinga common electrode; a second substrate having an active area; a sealpattern formed peripherally to said active area, and between said firstsubstrate and said second substrate; a liquid crystal layer between saidfirst substrate and said second substrate, and on the active area; anelectrode pattern encapsulated by said seal pattern on three sides ofthe electrode pattern and outside said active area; and an electricfield between said electrode pattern and said common electrode.
 2. Thedevice of claim 1, wherein the electric field is formed when saidelectrode pattern is applied with a voltage which is stepped down from acommon voltage applied to said common electrode.
 3. A liquid crystaldisplay device comprising: a first substrate having a common electrode;a second substrate having an active area; a seal pattern formedperipherally to said active area between said first substrate and saidsecond substrate, and having projected corner portions; a liquid crystallayer between said first substrate and said second substrate in saidactive area; an electrode pattern formed on the second substrate, theelectrode pattern completely embedded within a lengthwise portion of theseal pattern and directly covered by the seal pattern along three sidesof the electrode pattern; and an electric field between the electrodepattern and the common electrode.
 4. The device of claim 3, wherein saidelectrode pattern is between said seal pattern and said secondsubstrate.
 5. The device of claim 3, wherein said second substratecomprises: data lines and gate lines arranged in a matrix shape todefine pixel areas; a TFT at an intersection of a data line and a gateline; a protective film on the TFT; and a pixel electrode on saidprotective film.
 6. The device of claim 5, wherein said electrodepattern is between said seal pattern and said protective film.
 7. Thedevice of claim 5, wherein said electrode pattern is made of the samematerial as said pixel electrode.
 8. The device of claim 5, wherein saidelectrode pattern is formed at the same time as said pixel electrode. 9.The device of claim 3, wherein said electrode pattern is applied with avoltage which is stepped down from a common voltage applied to saidcommon electrode.
 10. The device of claim 3, wherein the electric fieldis formed by application of a voltage to the electrode pattern and thecommon electrode.